In various bio-measurements, the presence or absence and the amount of a substance to be detected, such as an antigen (or an antibody) is measured by detecting a biomolecular reaction, such as an antigen-antibody reaction. In this description, performing such a measurement, and determining a state, such as “positive” or “negative”, based on a result of such a measurement are collectively referred to as “analysis”.
For example, one of two substances that specifically bind to one another (such as an antigen, an antibody, an enzyme, a receptor, etc.) may be immobilized on a substrate, the other substance (which may be a substance to be detected, or a competing substance that competes with the substance to be detected in a sample) may be bound to the immobilized layer on the substrate, and the binding reaction may be detected to analyze the presence or absence and the amount of the substance to be detected in the sample.
Specifically, immunoassay is known, and examples thereof include: a sandwich method, which involves, in order to detect an antigen that is the substance to be detected contained in a sample, immobilizing an antibody that specifically binds to the antigen on a substrate, supplying the sample onto the substrate to have the antigen specifically bind to the antibody, adding a labeled antibody that specifically binds to the antigen and is provided with a label to have the labeled antibody bind to the antigen to form a so-called sandwich of antibody-antigen-labeled antibody, and detecting a signal from the label; and a competition method, which involves binding a labeled competing antigen to an immobilized antibody competitively with an antigen that is the substance to be detected, and detecting a signal from the label of the competing antigen that is bound to the immobilized antibody.
In the above-described sandwich method, the antigen that is the substance to be detected corresponds to “the other substance”. In the competition method, the competing antigen corresponds to “the other substance”. With the latter competition method, there is a relationship that a larger amount of the competing antigen bound to the immobilized antibody indicates a smaller amount of the antigen that is the substance to be detected, and therefore the amount of the antigen can be found from a level of the signal from the label, which corresponds to the amount of the competing antigen, based on the relationship.
Further, fluorescence detection methods are widely used as highly sensitive and simple measurement methods applicable to the above-described bio-measurements. In the fluorescence detection methods, a sample that is considered to contain a substance to be detected, which emits fluorescence when excited by light of a specific wavelength, is exposed to the excitation light of the specific wavelength, and the fluorescence emitted at that time is detected to check the presence of the substance to be detected. Further, in a case where the substance to be detected is not a fluorescent substance, it is widely practiced that a substance that specifically binds with the substance to be detected is labeled with a fluorescent colorant and is brought into contact with the sample, and then the fluorescence is detected in the same manner as described above to check the presence of the bond, i.e., the presence of the substance to be detected.
With respect to the above-described bio-analysis that uses optical techniques, reduction of a required time is desired, and various methods have been proposed for reducing a required time by efficiently causing a reaction at the reaction area. For example, U.S. Pat. No. 6,194,223 (hereinafter, Patent Document 1) proposes using an analysis chip having a microchannel and making a sample liquid flow down through the microchannel at a constant high speed, thereby speeding up the analysis. This type of analysis chip is also applicable to the above-described detection and quantitative analysis of a substance to be detected using the fluorescence detection.
In a case where the measurement as described above uses an immune reaction, an enzyme reaction, or the like, such reactions are highly temperature dependent, and therefore temperature control for accurately maintaining the reaction area at a predetermined temperature is performed during a measurement for diagnosis, etc., requiring high reliability. Japanese Unexamined Patent Publication No. 2010-139332 (hereinafter, Patent Document 2) discloses one example of an analysis device that involves such temperature control. To set the temperature of a reaction solution in a reaction vessel, which is the object of the temperature control, to a desired temperature, the device disclosed in Patent Document 2 measures the ambient temperature of the reaction vessel, in addition to the temperature of a constant temperature liquid forming a part of a temperature control means, and sets a target temperature of the constant temperature liquid depending on the ambient temperature to perform feedback control of the temperature of the constant temperature liquid based on the ambient temperature. Patent Document 2 also teaches heating the reaction solution with a heater, or the like, in place of the constant temperature liquid.